He said "oxygen." When you have liquid in the PET bottle you can squeeze all the air out before capping it with the carbonator, then add CO2, but with hops, I don't think you can do that, so there will be some O2 in there, but very little.

I have always assumed that the idea is to fill the container with co2, wait a bit for things to settle down in there and then purge through a top opening which should get most of the o2 out as it will have migrated to the top portion of the container. still some o2 but a lot less

That's not how gases work. Otherwise, basements would be deadly. :-)

excuse me, let me add 'In absence of any continued mixing' which, for all practical purposes doesn't happen in 'the real world'. and basements CAN be deadly. Think co2 fire extinguishers, or failing co2 bulk tanks for that matter. If you are in a basement with say 500lb of co2 in a tank and that tank suddenly empties that basement will very much be deadly. Why? because the co2 will displace all the other gases from the bottom up. That's why it works to put out fires. that's why a balloon filled with helium rises. That's why the myth buster guys can do the trick with the heavier than air gas in the fishtank and the boat made of foil (look it up, it's pretty cool). It's not perfect statification and any little tiny movement will mix the gases again but it does happen.

The sudden release of gas will push other gases out of the way, that is true. But in a closed system like a keg where there is no mixing, you will not see stratification of the gases, they mix evenly. And let's be clear, a CO2 extinguisher does not need to push all of the O2 out of the space - the atmosphere is ~21% O2. The amount of O2 required for sustained combustion varies by material, but in general people throw around the number 14% O2 to sustain burning. So the CO2 extinguisher only needs to get rid of 1/3 of the O2. For breathing, we collapse when the O2 level drops below ~8%, and suffocate in minutes if it is below ~5%. More importantly, CO2 levels above 5% cause problems, with immediate loss of consciousness somewhere above that (10%? 15%? I'm not sure). So again, not all of the O2 and other gases need to be evacuated from the space to be dangerous.

You might have posted pre-coffee, but you know this has nothing to do with what we're talking about.

Gases mix - the molecules move constantly (if the temperature is above absolute zero), and they move faster the warmer it is. There is so much space between molecules and they so rarely interact with each other that we can effectively say they do not interact. Given time and no stirring there will be an even distribution of each type of molecule throughout the given space.

It is not an oil/water analogy. It is blue water vs. yellow water. You can layer them as gently and carefully as you want in a closed container, but given time you will end up with green water.

alright, I will admit when I am wrong. course the fact that you can't displace all the o2 in a container with co2 is why I purge my kegs by filling with liquid and forcing that out with co2 so I was aware of this issue to some extent.

**EDIT**

so does this mean that the 'blanket of co2' argument is false? If I am reading and understanding this discussion correctly it means that more or less all of the o2 that was in my fermenter headspace to start with, less the amount removed by the dilution with co2 from fermentation and the amount removed by disolution into the liquid is still present at the close of fermentation. Which means that even a little stirring of a finished beer risks oxidation.

so does this mean that the 'blanket of co2' argument is false? If I am reading and understanding this discussion correctly it means that more or less all of the o2 that was in my fermenter headspace to start with, less the amount removed by the dilution with co2 from fermentation and the amount removed by disolution into the liquid is still present at the close of fermentation. Which means that even a little stirring of a finished beer risks oxidation.

More or less, the blanket of CO2 is a bad analogy. It gets the point across though

The O2 in your headspace is effectively gone - some of it will get pushed out due to vigorous fermentation, some of it will dissolve into the beer as the O2 in the beer is taken up by the yeast, and whatever is left is not enough to worry about.

The O2 in your headspace is effectively gone - some of it will get pushed out due to vigorous fermentation, some of it will dissolve into the beer as the O2 in the beer is taken up by the yeast, and whatever is left is not enough to worry about.

but what about racking into a keg?

Logged

The happiest people don’t necessarily have the best of everything; they just make the best of everything they have.

The O2 in your headspace is effectively gone - some of it will get pushed out due to vigorous fermentation, some of it will dissolve into the beer as the O2 in the beer is taken up by the yeast, and whatever is left is not enough to worry about.

but what about racking into a keg?

Unless you've filled it with liquid and pushed that out with CO2 (ala Mort), there is oxygen in the keg. If you've flushed it in this fashion you probably want to rack under pressure as opening the keg would defeat the purpose of flushing it, though I'm sure the flush is still beneficial.

If you have not flushed in Morts fashion, the O2 obviously gets displaced by the beer. The remaining amount in the headspace is minimized by purging it with CO2 several times, but not entirely eliminated.

The O2 in your headspace is effectively gone - some of it will get pushed out due to vigorous fermentation, some of it will dissolve into the beer as the O2 in the beer is taken up by the yeast, and whatever is left is not enough to worry about.

but what about racking into a keg?

Unless you've filled it with liquid and pushed that out with CO2 (ala Mort), there is oxygen in the keg. If you've flushed it in this fashion you probably want to rack under pressure as opening the keg would defeat the purpose of flushing it, though I'm sure the flush is still beneficial.

If you have not flushed in Morts fashion, the O2 obviously gets displaced by the beer. The remaining amount in the headspace is minimized by purging it with CO2 several times, but not entirely eliminated.

I've never worried too much about this. Never really had an issue.

Exactly - if it bothers you then fill the keg with starsan, push it out with CO2, and RDWHAHB.

He said "oxygen." When you have liquid in the PET bottle you can squeeze all the air out before capping it with the carbonator, then add CO2, but with hops, I don't think you can do that, so there will be some O2 in there, but very little.

I have always assumed that the idea is to fill the container with co2, wait a bit for things to settle down in there and then purge through a top opening which should get most of the o2 out as it will have migrated to the top portion of the container. still some o2 but a lot less

That's not how gases work. Otherwise, basements would be deadly. :-)

Breweries with basement fermentation areas need to have CO2 alarms, as the CO2 source will pool. I worked in a place with sources in the form vehicles, and the confined spaces had to be tested before entry (think the pits for hydraulic hoists) as the heavier gases would pool. The mixing of gases from diffusion is not instantaneous. http://en.wikipedia.org/wiki/Lake_Nyos

Good thing with CO2, at least, is that if you're in an area with excessive levels of it, you quickly feel breathless. (Not that you'd want to go down to a basement where it's pooled, but if you're aware of the effect and can easily escape, you've got built-in sensors for it.) That's not the case for other gasses -- for example, there are plenty of horror stories about people working with liquid nitrogen in enclosed spaces who never knew what hit them.

Right, like when I stick my head in my fermentation chest freezer to look at my beer and I nearly pass out from all the co2...

I did that on the first batch I made using a fermentation chest freezer. I stuck my head in to take a whiff of the ferment and got a lung full of CO2. That was one of those after-the-fact forehead-slapping moments where you realize how dumb you can be. Did the same thing many, many years ago when we were inhaling helium to make funny voices and I took an extra-long breath so that I could talk for a long time.

Right, like when I stick my head in my fermentation chest freezer to look at my beer and I nearly pass out from all the co2...

I did that on the first batch I made using a fermentation chest freezer. I stuck my head in to take a whiff of the ferment and got a lung full of CO2. That was one of those after-the-fact forehead-slapping moments where you realize how dumb you can be. Did the same thing many, many years ago when we were inhaling helium to make funny voices and I took an extra-long breath so that I could talk for a long time.

I almost fell off the catwalk on the Jack Daniels tour when I leaned out over the fermenting vats and took a big whiff.

Logged

Jeff Gladish, Tampa (989.3, 175.1 Apparent Rennarian)Homebrewing since 1990AHA member since 1991, now a lifetime member BJCP judge since 1995

I know, I pull my head out of the chest freezer thinking, why am I so out of breath? Then I realize, duh, I just breathed in a bunch of co2. Anyway, storing hop pellets? I feel like using old hops gives you the bitterness, but not the aroma and flavor aspects, leaving a grassy, vegetal thing that is not terribly enjoyable.